Meet 12-year-old Kaytlynn Welsch and her sister Heather, 10—some of the fastest (and youngest) endurance runners in the United States. The girls have competed in more than 160 endurance races in less than two years, and while a New York Times article asked if this was “too fast too soon,” the girls regularly see a doctor who reports they are in great condition.

Kaytlynn and Heather are coached by their father Rodney Welsch who started the girls in short children’s triathlons when they were seven. Welsch and his wife were both athletic and wanted their girls to be active. Because Kaytlynn and Heather were small for their age, they were disadvantaged in many sports…but not running.

A few years later, in 2010, Welsch began to enter his daughters in races up to 10k where they usually outran everyone in their age group and most women in their 20s and 30s. Then, in August 2012, Kaytlynn won the women’s division of a highly competitive 13-mile race in Waco, Texas. Heather finished third. Afterward, Kaytlynn was heralded as a “12-year-old trial running phenom” by Outside.

The girls hope to run in the Olympics, but they’ll have to wait several more years. The minimum age requirement for competitors is 16 years old.